Monitoring system capable of generating audible messages

ABSTRACT

A system for generating an audible message to a human includes an apparatus having an input for receiving an audio message. The audio message is stored in a memory. An output may be used for rendering the audio message. The apparatus further includes a microphone and a controller. If a sound is received via the microphone, the controller causes the stored audio message to be rendered via the output.

The invention relates to a system, in particular a baby monitor, forgenerating an audible message to a human.

Baby monitors typically include a baby unit and at least one parentunit. The baby unit is placed next to the bed of the baby. The unitincludes a microphone. Sounds received from the baby are sent from thebaby unit to the parent unit. Most baby units only send on the babysounds if the sound level is above a certain level. The parent unitincludes a speaker for rendering the sounds sent by the baby unit.

The functionality of baby monitors is increasing continuously. ThePhilips SBC SC467 baby monitor enables a human operator to adjust thesensitivity of the microphone. Only sounds above the chosen level aretransmitted to the parent unit. The parent unit also offers the optionto monitor the baby silently. In this case, the sound level of the babyis indicated visually and the speaker volume can be turned down to zerovolume level. To comfort the baby the parent can talk into a microphoneof the parent unit. The sound is sent to the baby unit. A speaker in thebaby unit renders the parent's voice.

It is an object of the invention to provide an improved system, inparticular a baby monitor, for generating an audible message to a human.

To meet the object of the invention, a system for generating an audiblemessage to a human includes an apparatus that includes: a microphone; aninput for receiving an audio message; a memory for storing a receivedaudio message; an output for rendering an audio message; and acontroller for, in response to detecting a sound received via themicrophone, causing the stored audio message to be rendered via theoutput.

The inventor had the insight that the comforting option of the knownbaby monitor only works if the parent is present and able to respond toa cry from the baby. If the parents are away the voice of a baby sittermay not have the desired effect. If the parents are asleep, usually thebaby has to cry sufficiently loud to wake up the parent. The parentcould then use the known baby monitor to comfort the baby without havingto get out of bed. However, by this time the distress of the baby mayalready be too high for comforting sounds to have an effect. Therefore,in the system according to the invention the apparatus that detects thesounds (e.g. of a baby) also generates the (comforting) audio messageautomatically. The message is recordable and stored in a memory of theapparatus. In one embodiment, the apparatus is preferably a baby unit.This may be a conventional baby unit with the described functionalitybeing added. It may also be a stand-alone device, such as lullaby-toy. Aparent can record the message and so optimally soothe the baby. Thesystem may also be used for other functions than acting on a baby sound.In particular, the system may be used for alerting snorers or acting onsleep apnea.

In another embodiment, the apparatus includes a signal level detectorfor detecting a signal strength of an audio signal received via themicrophone; the controller being operative to cause the rendering inresponse to the signal level detector detecting that the signal strengthexceeds a threshold. In this way only sounds with a sufficient strengthtrigger the playback of the message. Preferably, the apparatus includesa user interface for enabling a human operator to determine thethreshold.

In another embodiment, the apparatus includes a sound discriminator fordetecting audio signals received via the microphone representative of ahuman sound; the controller being operative to cause the rendering inresponse to a trigger from the discriminator. The discriminator may beimplemented in any suitable way, for example using a frequency bandfilter to extract frequencies that are likely to include the humansound. Also pitch detectors or speech recognizers may be used for moreaccurate detection. In a preferred embodiment, sounds that aresufficiently distinct from baby sounds and/or snoring can be filteredout avoiding undesired replay of the message.

In another embodiment, the input is coupled to the microphone forenabling a human operator to record the audio message. This is aneffective way of recording the message. Alternatively, the message maybe received from another apparatus. For example, in a baby monitorsystem the message may be received from the parent unit.

In another embodiment, the apparatus of the system includes a baby unitfor rendering the stored audio message to a baby in response to a soundfrom the baby and the system further includes a parent unit; the babyunit and parent unit including respective communication means forestablishing communication between the units; the controller of the babyunit being operative to cause the stored audio message to be renderedimmediately after detecting the sound, and to cause an alarm signal tobe sent to the parent unit only after the sound has been detected for apredetermined period; and the parent unit including an output foralerting a human; and a parent unit controller for causing the human tobe alerted in response to receiving the alarm signal from the baby unit.In this way, the baby unit acts like a first line soother. If notsuccessful within the predetermined period, the parents are stillalerted. If successful, parents do not need to be woken up or do notneed to take the effort to walk to the baby. The period is configurable.

In another embodiment, the sound discriminator is operative todistinguish between at least a first and second category of sound of thebaby; the baby unit controller being operative to send the alarm signalto the parent unit for a sound of the first category only after thesound of the first category has been detected for a predetermined periodand to send the alarm signal to the parent unit for a sound of thesecond category in immediate response to detecting a sound of the secondcategory. In this way, automatic soothing occurs for the first categoryof sounds (e.g. a slight moaning of the baby) only followed by an alarmif the sound remains for a prolonged period. For a second category ofsound requiring urgent attention (e.g. distress of the baby, sleepapnea, etc) the parent is alerted immediately.

In another embodiment, a sound that can be detected is sleep apnea. Thedisorder can be life-threatening, especially for babies. Sleep apnea isalso serious for adults and can cause tiredness due to lack of sleep.The system according to the invention can alert the sleeper with theprerecorded message.

In another embodiment, the sound discriminator is operative to detect atleast one further human sound (e.g. snoring) distinct from sleep apnea;the controller being operative to cause rendering of the audio messageat distinct volume levels, where a higher volume level is used renderingthe message in response to detection of sleep apnea than is used forrendering the message in response to detecting the further human sound.Since sleep apnea is a serious disorder, alarm is raised at a highlevel.

In another embodiment, the memory is operative to store at least onefurther audio message; the message to be rendered being selectable by ahuman and/or selected by the controller. The further message may be apre-recorded message of a human recordable message. The operator orcontroller may select a distinct message as a response to a respectivedistinct sound detected by the apparatus. In order to keep the babyentertained a number of different sounds or recorded messages may beplayed in any sequence, otherwise the baby may learn that it is not thereal parent soothing him, or at least lose interest and start cryingagain. A vast amount of pleasant sounds may be present in the device.

These and other aspects of the invention are apparent from and will beelucidated with reference to the embodiments described hereinafter.

In the drawings:

FIG. 1 shows a block diagram with a standalone apparatus, and

FIG. 2 shows a block diagram of a system with two communicatingapparatuses, in particular a baby unit and a parent unit.

FIG. 1 shows a block diagram of the system according to the invention.In the example of FIG. 1 the system includes one apparatus 100. Theapparatus 100 may be incorporated in an existing device. For example, ifthe apparatus according to the invention is used for soothing a baby orchild, it may be incorporated in a device that is typically present in ababy's/child's bedroom. This could be a toy, such as a lullaby toy, oran electronic device like an audio system or an alarm clock. In apreferred embodiment, the apparatus is incorporated in a baby unit of ababy monitoring system. If the apparatus is used for alerting a human inresponse to detecting snoring or sleep apnea, the apparatus may beincorporated in an electronic device, such as an alarm clock. Theapparatus includes a microphone 110 for receiving sounds. For manyapplications this can be a conventional microphone as, for example, usedin baby monitors. For certain applications, e.g. detecting snoring ofone person and ignoring sounds of other persons in the same area, it ispreferred to detect sound in a more directional way. To this end, in apreferred embodiment the microphone is a directional microphone. In analternative embodiment, a beamformer is used. Directional microphonesand beamformers are well-known. An example of a beamformer is describedin “IEEE ASSP Magazine” of April 1988, pages 4 to 24. The apparatusfurther includes an input 120 for receiving an audio message, e.g. of aparent. In many applications the input will be connected to themicrophone 110 to enable a human to speak or sing the message. The inputmay include an A/D converter for converting the message to a suitabledigital representation. The input may also include a compressor forcompressing the digital representation to reduce storage requirements.Such converters and compressors are well-known and will not be describedfurther. Other ways of inputting the message are also possible, e.g. viaa communication system to another apparatus within or outside the systemor via removable storage medium, such as a solid-state memory. Thereceived audio message is stored in a memory 140. Preferably, the memoryis non-volatile, e.g. based on flash or MRAM. The apparatus alsoincludes an output for rendering the audio message. The output mayinclude a conventional decompressor and D/A converter. Typically theapparatus includes or is connected to a loudspeaker 160.

The apparatus further includes a controller 130 that is operable tocause the stored audio message to be rendered via the output, if a soundhas been detected via the microphone. In a simple apparatus thecontroller may be implemented using dedicated hardware components. In amore advanced apparatus, the controller may be an embedded controllerfor controlling also other functions of the apparatus. The controllermay even be a signal processor (such as a DSP) and be able to performthe described compression/decompression functions, beamforming and othersignal processing functions as will be described below in more detail.Such a more advanced controller is operated under control of a softwareprogram. The program may be fixedly embedded in the controller. It mayalso be loaded from a (preferably) non-volatile memory, such as memory140. The apparatus may include also a volatile memory, such as RAM, usedduring the operation of the system and erased each time the apparatus isswitched off.

In an embodiment according to the invention, the apparatus includes asignal level detector 171 for detecting a signal strength of an audiosignal received via the microphone 110. It may be comprised in thesignal processing block 170, e.g. as a software module running on thesignal processing block 170 being e.g. a digital signal processor. Thedetected signal strength may be based on the amplitude of a singlesample. Preferably, signal strength is determined based on a consecutivesequence of samples, e.g. covering 10 msecs to 1 sec. Using a longerperiod decreases the chances of acting on an irrelevant sound peak. Atoo long period increases the risk of missing the sound of interest.Preferably, a majority voting is used on a series of those shortsequences at samples taken within an interval of in total 10 secs. totwo minutes. Persons skilled in the art can choose the period and/or themajority voting interval optimally for each application, depending onthe characteristics of the sound of interest. The signal level detector171 compares the signal strength to a predetermined threshold that maybe stored in the memory 140. If the signal level detector detects thatthe signal strength exceeds a predetermined threshold it activates therendering of the stored audio message. It will be appreciated that thefunction of the signal level detector 171 may be executed by thecontroller 130. Preferably, the apparatus includes a user interface f orinteraction of the apparatus with a user. Input of a user may bereceived via buttons or wheels or any other suitable input means,including a remote control and voice control. Output may be given viaLEDs, LCD displays, or any other suitable means. Advantageously, theuser can configure parameters of the signal level detector, such as thethreshold level and minimum period in which the signal must be above thethreshold. In this way, the apparatus can be optimally configured for aspecific person and can also be configured for different applications,such as detection of baby cries, snoring detection and detection ofsleep apnea. For sleep apnea, the detection may be triggered exactly theother way around. If no breathing sound is detected for a predeterminedperiod, e.g. the microphone 110 picks up the relative silence of thebedroom during the period, or the characteristic sound patterns of sleepbreathing are lost during the period, a trigger is given, as will bedescribed in more detail below.

In an embodiment according to the invention, the apparatus includes asound discriminator 172 for detecting audio signals received via themicrophone representative of a human sound, as contrasted to non humansounds. In FIG. 1, the sound discriminator 172 is incorporated into thesignal processing block 170 also used for the signal level detection. Ifsuch a human sound is detected, a trigger is given to the controller130. In response, the controller causes the rendering of the audiomessage. By detecting sounds that could be from a human, other soundscan be ignored reducing the number of false renderings of the message.The sound detection can be done in many different ways. In a simpleembodiment, the sound detection filters out frequencies that are mostlikely not generated by human mouths, e.g. using a filter that passesthrough frequencies in the range of 100 to 3000 Hz. In a more advancedembodiment, in particular useable for detecting baby cries, the sounddetection includes detecting a pitch of the received sound. If thedetected pitch falls within the range of pitches normal for babies (e.g.300 to 900 Hz.) a trigger is issued. Pitch detection can be done in thefollowing way. Voiced speech can be modeled as a train of Diracimpulses, representing an excitation of the vocal cords that is filteredby a filter representing the resonances in the vocal tract, the glottalsource spectrum, and the radiation load spectrum. The pitch isdetermined by the period of the Dirac impulses. The first peak in theaudio spectrum of the autocorrelation of the audio signal can be usedfor determining a pitch of an audio signal. Using the autocorrelationmethod, the pitch T is the time shift which maximizes the correlation:

${C\left( {k,T} \right)} = \frac{\left( {ik}^{T} \right){i\left( {k + T} \right)}}{{{({ik})i}}{\left( {k + T} \right)}}$where the in-product is typically calculated over a certain number ofsamples S of the audio signal i(k) and the small T in the exponent ofi(k) denotes a transposition. Many other ways of detecting pitch areknown from speech processing applications, such as speech recognitionand speech synthesis. Preferably, the sound discriminator is able todistinguish between different sounds. It may do this using speechrecognition techniques that by definition are able to recognizedifferent sounds, both voiced as well as unvoiced sounds. In particular,for baby monitoring applications, the sound discriminator is able todistinguish between at least two categories of baby sounds. Sounds maybe different in many ways, e.g. being completely different sounds infrequency and sound/non-sound intervals, like snoring and sleep apnea.They may also be different in emotion, e.g. a moaning baby cry and adistressed baby cry. Such a difference in emotion may be detectable fromthe amplitude of the sound. WO 02/37474 describes many differentemotions and ways of recognizing the emotions. These techniques may beemployed in the system according to the invention to come to an accurateclassification of sounds. To this end also a video camera may be used asa further input to assist in the classification.

FIG. 2 shows a preferred embodiment, wherein the system in addition tothe baby unit 100 of FIG. 1 also includes a parent unit 200. If sodesired, the system may include multiple baby units and/or multipleparent units. The elements of the baby unit indicate with a samereference number as used for FIG. 1 perform the same function asdescribed with reference to FIG. 1. The baby unit and parent unitinclude respective communication means 190, 290 for establishingcommunication between the units. The communication may be in anysuitable form, for example as already used in baby monitoring system.Preferably, the communication is wireless. For basic operation it issufficient if the communication is one-directional (from the baby unitto the parent unit). For more advanced applications, it is preferred touse bi-directional communication. In the preferred embodiment, thecontroller 130 of the baby unit immediately causes the stored audiomessage to be rendered locally if it detects a sound. It sends an alarmsignal to the parent unit via the communication means 190 only after thesound has been detected for a predetermined period. A human operator mayconfigure the period in which the baby unit does not alert the parentunit. The parameter may be stored in the memory 140. The configurationmay take place via the user interface 180 of the baby unit. It may alsotake place via a user interface 280 of the parent unit, if two-waycommunication is possible. The alarm signal may be sent in any suitableform. Advantageously, the baby unit simply passes on the sound that itreceives (e.g. the baby cries). So, it does not pass on the sound aslong as the period has not expired. Passing on the baby sounds afterexpiry of the period enables the parent to accurately assess thedistress of the baby. The sound of the baby may be passed on in ananalogue or digital form. The alarm signal may also be a digital code,such as a short digital message, to trigger the parent unit. The parentunit includes an output 250 for alerting a human. Preferably, the outputis connected to a speaker 260. If the alarm is received via thecommunication means 290 as a digital trigger signal (e.g. message), theparent unit may issue any specific alarm signal, e.g. produce an alarmring tone or produce a flashing light. Such signal may be issued via auser interface 280 of the parent unit. The controller 230 of the parentunit is responsible for causing the human to be alerted in response toreceiving the alarm signal from the baby unit. The controller may be anysuitable microcontroller or processor. It may come with embeddedsoftware or the software may be loaded from a (preferably non-volatile)memory, such as a memory 240. The parent unit may also include amicrophone (210) or be connected to it. Via this microphone a parent maybe able to talk directly to the baby, input the message to be stored inthe baby unit, etc. The microphone may be connected to an input 220 thatmay include an A/D converter and audio compressor. The parent unit mayalso be incorporated in another device, such as a television, orportable device like a mobile phone, or personal digital assistanceassistant (PDA).

As described above, the sound discriminator 172 may be able todistinguish between at least a first and second category of sound of thebaby. For a baby monitoring system, the first category of sound includesany baby sound that does not require immediate attention of a parent (orcaretaker), e.g. moaning sounds, and sounds with a low distress factor.For sounds of this category, the baby unit controller 130 immediatelyrenders the stored message, but only after the sound has been detectedfor the predetermined period it sends the alarm signal to the parentunit. In this way, the system automatically tries to sooth the babywithout alarming the parent (yet). Sounds of the second category aresounds that may require immediate attention. Such sounds may includebaby cries with high distress (e.g. high volume) or sleep apnea. Thecontroller 130 sends an alarm signal to the parent unit immediately whena sound of the second category is detected. It will be appreciated thatmore categories can be defined, each with a respective response at thelocal apparatus and/or remote apparatus.

As described above, the sound discriminator is preferably operative todetect sleep apnea. This can be useful for babies, where sleep apnea isa major cause of cot-deaths, as well as for adults. During sleep, thebody is relatively at rest. The heartbeat and body temperature drop.This process is completely automatic. People with sleep apnea havetrouble with the breathing process during their sleep. Sometimes theystop breathing for a minute and wake up in panic. Sleep apnea can becharacterized as repeated periods of total or partly blocking of the airpassage longer than 10 seconds, causing oxygen deprivation. The disordercan be life-threatening, especially for babies. Often babies havedifficulties during their sleep. Difficulties with breathing are amongthese. Fortunately, most babies wake up automatically. Cot-deaths occurmainly in the first two years of a baby. Particularly during this periodit is important that parents can intervene if breathing stops too long.Children or adults with sleep apnea wake up all the time andconsequently don't get enough rest during the night. They are very tiredduring the day. Most of the times, the body turns into anemergency-state when deprived of oxygen for a while. For older childrenand adults it is preferred that the system alerts them in time beforethe oxygen-deprivation occurs. A minor disturbance of the personinvolved may be enough to restart the breathing process without fullywaking the person. Since apnea is serious, it is preferred that ifbreathing is not restarted quickly, the audio message is rendered at ahigh volume level. As described the audio message may be rendered to theperson itself, or in the case of the baby monitoring system, to theparents through the parent unit. The baby unit may then also still issuethe message to awaken the baby in case the parents are not present orasleep too fast (or the parent unit is switched off). The high volumelevel is higher than used for rendering an audio message for othersounds.

One of the other sounds that the system can detect in a preferredembodiment is human snoring. Snoring can be described as breathingduring sleep with a rough hoarse noise due to vibration of the uvula andsoft palate. In particular for snoring, it is desired that only thesnorer is stimulated to move a bit so that the snoring stops. To achievethis, the audio message is rendered at a level lower than usually usedfor waking a human, using a conventional loudspeaker. In such a case,the connection between the output 150 and the loudspeaker 160 may be aconventional wired connection. It is also possible to use a loudspeakerthat can be detached from the apparatus. This can be achieved by using alonger wire. Advantageously, a wireless connection is used between theapparatus and the loudspeaker. This is particularly useful if theapparatus is used for alerting a snorer. In such an application theloudspeaker may be a loudspeaker that can be put on or under the pillowor at least very near to the snorer so that no other people in the roomare alerted. Such loudspeakers in itself are known and typically used bypeople who listen to music or a book while resting on bed. In apreferred embodiment, the loudspeaker is an ear-mounted loudspeaker asis well-known from loudspeakers for people with a hearing disorder. Ifthe loudspeaker can be positioned very near the person involved thevolume level can be chosen such that the person involved is alerted, butthat no other people are disturbed. As an alternative to or in additionto alerting the human using sound, also other stimuli may be used. Foralerting a snorer or person with sleep apnea, preferably a vibrator isused. Vibrators are well-known for example from mobile phones.

The description of the system given above focuses on using one audiomessage for alerting a human. It will be appreciated that the memory 140may be able to store several audio messages of which at least one isrecordable. The other messages may be recordable or prerecorded. Using asystem with multiple messages, the message to be rendered may beselectable by a human via the user interface. In a simple embodiment,only one message can be rendered by the system, where the human canselect which one. In a more advanced embodiment, the system is able torender different messages for different events. For example, a differentmessage for snoring than for sleep apnea. In such a system the user canpreferably select for each event a message to be rendered.Alternatively, the controller selects the message most suited for theevent, e.g. a soothing message if the person should continue sleepingand an alarming message if the person should wake up (or partly awakeup). Preferably, the user can also select a volume level for renderingfor each event or each message. The settings selected by the user can bestored in the memory 140 and applied by the controller during rendering.

It should be noted that the above-mentioned embodiments illustraterather than limit the invention, and that those skilled in the art willbe able to design many alternative embodiments without departing fromthe scope of the appended claims. In the claims, any reference signsplaced between parentheses shall not be construed as limiting the claim.Use of the verbs “comprise” and “include” and its conjugations does notexclude the presence of elements or steps other than those stated in aclaim. The article “a” or “an” preceding an element does not exclude thepresence of a plurality of such elements. The invention may beimplemented by means of hardware comprising several distinct elements,and by means of a suitably programmed computer. In the device claimenumerating several means, several of these means may be embodied by oneand the same item of hardware. The mere fact that certain measures arerecited in mutually different dependent claims does not indicate that acombination of these measures cannot be used to advantage.

1. A system for generating an audible message for a monitored human; thesystem including an apparatus including: a microphone; an input forreceiving different audio messages; a memory for storing the receiveddifferent audio messages; an output for rendering the different audiomessages; and a controller for, in response to detecting a soundreceived via the microphone, causing the stored different audio messagesto be rendered via the output in different sequences to reduce alikelihood that the monitored human may learn that the rendereddifferent messages are stored.
 2. The system as claimed in claim 1,wherein the apparatus includes a signal level detector for detecting asignal strength of an audio signal received via the microphone; thecontroller being operative to cause the rendering in response to thesignal level detector detecting that the signal strength exceeds apredetermined threshold.
 3. The system as claimed in claim 1, whereinthe apparatus includes a sound discriminator for detecting audiosignals, received via the microphone, representative of a human sound;the controller being operative to cause the rendering in response to atrigger from the discriminator.
 4. The system as claimed in claim 1,wherein the input is coupled to the microphone for enabling a humanoperator to record the audio message.
 5. The system as claimed in claim1, wherein the apparatus includes a baby unit for rendering the storedaudio message to a baby in response to a sound from the baby.
 6. Asystem for generating an audible message for a human; the systemincluding an apparatus including: a microphone; an input for receivingan audio message; a memory for storing the received audio message; ababy unit for rendering the stored audio message to a baby; a controllerfor, in response to detecting a sound from the baby received via themicrophone, causing the stored audio message to be rendered via the babyunit; and a parent unit; the baby unit and parent unit includingrespective communication means for establishing communication betweenthe baby unit and parent unit; the controller being operative to causethe stored audio message to be rendered immediately after detecting thesound, and to cause an alarm signal to be sent to the parent unit onlyafter the sound has been detected for a predetermined period; and theparent unit including an output for alerting a human; and a parent unitcontroller for causing the human to be alerted in response to receivingthe alarm signal from the baby unit.
 7. The system as claimed in claim6, wherein the system includes at least one user interface for enablinga human operator to configure the predetermined period.
 8. A system forgenerating an audible message for a human; the system including anapparatus including: a microphone; an input for receiving an audiomessage; a memory for storing the received audio message; a baby unitfor rendering the stored audio message to a baby; a controller for, inresponse to detecting a sound received via the microphone, causing thestored audio message to be rendered via the output; and a sounddiscriminator for detecting audio signals, received via the microphone,representative of a human sound; the controller being operative to causethe rendering in response to a trigger from the discriminator; whereinthe sound discriminator is operative to distinguish between at least afirst and second category of sound of the baby; the controller beingoperative to send an alarm signal to a parent unit for a sound of thefirst category only after the sound of the first category has beendetected for a predetermined period and to send the alarm signal to theparent unit for a sound of the second category in immediate response todetecting a sound of the second category.
 9. The system as claimed inclaim 3, wherein the sound discriminator is operative to detect sleepapnea by detecting at least one of silence.
 10. The system forgenerating an audible message for a human; the system including anapparatus including: a microphone; an input for receiving an audiomessage; a memory if or storing the received audio message; a baby unitfor rendering the stored audio message to a baby; a controller for, inresponse to detecting a sound received via the microphone, causing thestored audio message to be rendered via the output; and a sounddiscriminator for detecting audio signals, received via the microphone,representative of a human sound; the controller being operative to causethe rendering in response to a trigger from the discriminator; whereinthe sound discriminator is operative to detect at least one furtherhuman sound distinct from sleep apnea; and wherein the controller isoperative to cause rendering of the stored audio message at distinctvolume levels, where a higher volume level is used rendering the storedaudio message in response to detection of the sleep apnea than is usedfor rendering the stored audio message in response to detecting thefurther human sound.
 11. The system as claimed in claim 10, wherein thefurther human sound is human snoring.
 12. The system as claimed in claim1, wherein the memory is operative to store at least one further audiomessage; the message to be rendered being selectable by a human and/orselected by the controller.
 13. The system as claimed in claim 3,wherein the sound discriminator is operative to detect sleep apnea bydetecting loss of characteristic sound patterns of sleep breathing. 14.The system as claimed in claim 1 wherein, in response to detectingsilence, the controller is configured to render one of the storeddifferent audio messages at higher volume than other stored differentaudio messages to awaken the monitored human.
 15. The system as claimedin claim 1 wherein, in response to detecting snoring by the monitoredhuman, the controller is configured to render one of the storeddifferent audio messages at lower volume than other stored differentaudio messages to prevent awakening the monitored human.
 16. The systemas claimed in claim 15, further comprising a vibrator configured to beactivated upon detection of the snoring.